The Queen’s 70 years as sovereign has seen 14 prime ministers, from Second World War statesman Sir Winston Churchill to Boris Johnson, and now she is set to welcome her 15th.
Political leaders have consistently paid tribute to the monarch for her sage advice and impressive knowledge of home and world affairs during her private weekly audiences with her PMs.
Sir Winston, her first prime minister, is thought to be her favourite.
He greeted the young, grieving monarch back on British soil after her sudden return from Kenya on the death of her father, King George VI.
When Sir Winston retired in 1955, the Queen sent him a hand-written letter telling him how much she missed him and how no successor “will ever for me be able to hold the place of my first Prime Minister”.
Sir Winston had nurtured her through the early years, giving her invaluable advice.
The Queen’s relationship with the starchy Sir Anthony Eden was certainly more formal, while Harold Macmillan was an urbane figure in contrast to the monarch who is a countrywoman at heart.
However, on one occasion, rather than discussing affairs of state at one of their audiences, the Queen and Mr Macmillan could be seen huddled over a transistor radio as US astronaut John Glenn was hurtling through space.
Sir Alec Douglas-Home reportedly met with royal approval.
An aide said: “He was an old friend. They talked about dogs and shooting together. They were both Scottish landowners, the same sort of people, like old schoolfriends.”
Harold Wilson endeared himself to the Queen. “They got on like a house on fire,” one long-standing member of the Labour Party said.
He used to join members of the royal family for riverside picnics at Balmoral.
However, Sir Edward Heath is said to have struggled with small talk and their weekly audiences have been described as “frosty”.
James Callaghan managed to establish a warm rapport.
He said about the Queen: “One of the great things about her is that she always seems able to see the funny side of life. All the conversations were very enjoyable.”
But things were very different with Margaret Thatcher, who reportedly found the traditional September weekend at Balmoral painful.
One observer wrote: “A weekend in the country with aristocrats who enjoy riding, shooting, sports and games is Thatcher’s idea of torture.
“But her dread of the weekend receded as the two women became somewhat more comfortable with one another.”
Baroness Thatcher also could not abide the charades that she was expected to play after dinner at Balmoral and the Queen later, at a gathering of six of her premiers, joked about “the party games which some of you have so nobly endured at Balmoral”.
When Baroness Thatcher died in April 2013, the Queen took the unusual step of attending her ceremonial funeral – a personal decision and an indication of the Queen’s respect for her first – and at the time her only – female prime minister.
Sir John Major was popular with the royal family, and the Queen in particular, largely because of the genuine concern he expressed for the welfare of the two young princes William and Harry, first on the divorce of their parents and then on the death of their mother, Diana, Princess of Wales.
Sir Tony Blair was described in some palace quarters as a “head of state-in-waiting”, and there were courtiers who were not happy by what they saw as his encouragement of a “people’s monarchy”.
Neither Sir Tony, who later revealed details of his private conversations with the Queen in his memoirs, nor Gordon Brown, who was reported to have a good but formal relationship with the royals, were invited to the Duke and Duchess of Cambridge’s wedding in 2011.
A red-faced David Cameron was forced to make a grovelling apology to the Queen in 2014 after his “purr-gate” blunder.
Mr Cameron was caught on camera telling then New York mayor Michael Bloomberg that the monarch had “purred down the line” when he telephoned and told her the result of the Scottish independence referendum.
Theresa May was the second female prime minister of the Queen’s reign – taking up her post in July 2016 in the wake of the Brexit vote, more than a quarter of a century after Mrs Thatcher stood down.
Ahead of the Platinum Jubilee, Mrs May told the House of Commons: “She has seen prime ministers come and go, I was number 13.”
She added: “She has greeted us all with charm and consideration and with an impressive knowledge and understanding of the issues of the day.”
Mrs May attempted an impression of the Queen as she recalled how the head of state was driving her to a BBQ in the Scottish Highlands when they came across a large stag.
“Her Majesty slammed on the brakes and said: ‘What’s he doing here?’.”
She added: “She couldn’t understand why he had come down so low. She knew the countryside, she knew its animals.”
Mrs May’s premiership ended in 2019 after she endured a torrid time dogged by the issue of Brexit. She was succeeded by Boris Johnson.
Mr Johnson was only a few hours into his post when he revealed what was said in his audience with the Queen as he accepted her invitation to form the next Government and become PM.
A correspondent for Euronews NBC said the outspoken politician claimed the monarch quipped “I don’t know why anyone would want the job”.
A few months into his premiership, Mr Johnson apologised to the Queen after the Supreme Court ruled his advice to her – imparted by Commons Leader Jacob Rees-Mogg at Balmoral – to prorogue Parliament for five weeks had been “unlawful”.
Another apology to Buckingham Palace came from Downing Street amid the pandemic when two staff leaving events were held at Number 10 on April 16 2021, the eve of the Duke of Edinburgh’s funeral.
Sue Gray’s report into the partygate scandal later revealed that staff carried on drinking at Number 10 the night before Philip’s funeral until the early hours, with the last person not leaving until 4.20am.
On April 17, the Queen sat alone in mourning for her late husband amid strict Covid restrictions, with the congregation limited to just 30 people.
Mr Johnson revealed during a Parliamentary tribute to the Queen in her Jubilee year that his regular meetings with the monarch were always “immensely comforting, because she has seen the sweep of it”.
His departure will see the Queen, who is in the Platinum Jubilee year of her reign, welcome her 15th PM.